CN101790967B - Culture method of early-breeding seedlings of Charybdis japonica - Google Patents

Abstract

The invention is a method for cultivating early multiplication seedlings of japonica, which is characterized in that it comprises the steps of cultivating brood crabs, cultivating oviposit crabs, cultivating larvae and the like. The present invention aims at the reproductive biological characteristics of Japanese crab, utilizes the existing facilities of industrialized seedling cultivation of river crab, and through technical means such as regulation of ecological conditions, reasonable baiting, disease prevention and control, etc., cultivates the early breeding seedlings of Japanese crab required for breeding production, It has a long growth period and has a large size when it comes to the market, which can significantly improve economic benefits. Experiments have proved that using the present invention can realize the industrialized cultivation of early multiplication seedlings of Japanese squid, can solve the problem that the cultivation of Japanese squid in seawater ponds in coastal areas relies on natural seedlings, and can make full use of existing shrimp and crab nursery facilities and seawater aquaculture ponds , improving the economic benefits of mariculture in coastal areas has important economic and social significance. The invention has the characteristics of scientific rationality, low investment and high practicability.

Description

A kind of cultivating method of early multiplication seedling of Japanese catfish

technical field

The invention relates to the technical field of seedling breeding of crustaceans, in particular to a method for cultivating early-propagating seedlings of Japanese clams.

Background technique

Charybdis japonica belongs to Crustacea, Portunidae, and the genus Charybdis japonica. Its shape is similar to that of blue crabs, with large individuals and bright colors. Japanese crab meat is delicious, nutritious, and has the effects of clearing heat, nourishing, and reducing swelling, and is very popular among consumers. Japanese crab also has high industrial value. Its carapace is rich in chitin. In addition, monosodium glutamate can be extracted from crab shells, and crab shells can be ground as feed for poultry. It is a large marine crab with high economic value. There is a great demand in the market. Due to the excessive fishing in recent years, the amount of natural resources is depleting day by day, which is far from meeting people's needs, and the supply of products is in short supply. Therefore, it is necessary to vigorously carry out the artificial breeding of Japanese catfish. The breeding season of Japanese crab is from May to September, and the crab seedlings produced can be listed on the market at the beginning of the next year after about half a year of growth, and the price of centralized listing is not high. Among the currently published patents related to the field of crustacean seed breeding technology, it has been related to Chinese mitten crab, Portunus trituberculatus, crayfish, Litopenaeus vannamei, and freshwater shrimp in the crustaceans of the aquatic economy. There is no technical disclosure about the cultivation method of early multiplication seedlings of Japanese catfish.

Contents of the invention

The technical problem to be solved by this invention is to provide a kind of new method for cultivating the early multiplication seedlings of Japanese catfish for the deficiencies in the prior art; It has a long growth period and a large market size, can significantly improve economic benefits, and can solve the problem that seawater ponds in coastal areas rely on natural seedlings.

The technical problem to be solved by the present invention is achieved through the following technical solutions. The present invention is a kind of cultivating method of early multiplication seedling of Japanese catfish, it is characterized in that, its steps are as follows:

(1) Preparation of cultivation pond: Disinfect the cultivation pond with potassium permanganate. After disinfection, wash the cultivation pond with sea water to remove potassium permanganate; ～15cm of sand, and there is a drainage outlet on the cultivation pond where the sand is not spread; use sterilized tiles, hollow bricks or bamboo rafts to build shelters at the bottom of the sand-sprayed cultivation pond for the parent crabs to inhabit; inject deep 60 cm into the cultivation pond. ～80cm seawater with salinity 26～30 and pH 8.1～8.5;

(2) Cultivation of brood crabs: Take Japanese crab brood crabs with strong physique, complete appendages, and a shell length of more than 5cm. The ratio of male to female is 3:1, and sterilize them by soaking in 200-300mg/L formalin seawater solution and rinse with clean water. Afterwards, put them into the breeding pool for parent crab cultivation, and the cultivation density is 2 to 3/m ² ; during the parent crab cultivation period, the light is less than 1000 lux, and a small amount of air is added; when the parent crabs are cultivated, they are first cultured at natural water temperature for 2 to 3 days; Raise the temperature by 0.5-1°C to 14°C and maintain constant temperature cultivation. The cultivation time at this stage is 20-25 days; then further increase the water temperature to 20°C and cultivate for 15-20 days; The main bait, the feeding amount is 10-25% of the body weight of the brood crab; move the brood crab with eggs to the holding pond;

(3) Cultivation of oviposit crabs: the setting conditions of the oviposit crab temporary breeding pond are the same as those in the cultivation pond, or without sanding; the oviposit crabs enter the pool after being sterilized; they are cultured at natural water temperature for 2 to 3 days; After the range of ℃ rises to 23 ℃, maintain constant temperature cultivation, and cultivate at this stage for 12 to 14 days; the amount of bait to be fed is 2 to 10% of the body weight of the oviposit crab; check the development of the embryo, when the embryo is dark gray and black, and the heartbeat reaches an average of 170 When ~180 times/min, prepare to move the pool;

(4) Nursery pool preparation: Disinfect the nursery pool with potassium permanganate. After disinfection, use 200-mesh sieve silk screen to filter seawater to flush the nursery pool to remove potassium permanganate, and inject 200-mesh sieve silk screen to filter seawater to water depth in the nursery pool. 70-80cm, the initial water temperature is 22-23°C, then add 2-5g/m ³ EDTA ₂ Na salt to eliminate heavy metal ions, and then add unicellular algae to a density of 120,000-150,000/m ³ water body, and hang them in the nursery pool cage;

(5) Cultivation of larvae: With nystatin or potassium permanganate seawater solution, the oviposit crabs prepared in step (3) to move the pool are disinfected and bathed, then washed with seawater and then put into cages to row young, and each cage is put in one, And put eggs with similar color in the same pond; when the density of larvae in the nursery pond reaches 100,000 to 150,000/m ³ water body, move the oviposit crabs to another nursery pond and continue to row young; After the 6th stage of molting metamorphosis, it develops into megalopa, and the megalopa metamorphoses into stage I juvenile crabs after cultivation; after each stage of molt metamorphosis, the water temperature is increased by 0.5-1°C; after all metamorphosis into megalopa, stop Heat the water to gradually reduce the water temperature to the natural water temperature; the light intensity for larvae cultivation is 3000-10000 lux, the water salinity is 26-27, and the pH is 8.1-8.4; when cultivating, change water, aerate and feed as needed; when daphnia larvae After metamorphosis into megalopa, set up polyethylene mesh or scallop culture cages in the nursery pond for the larvae to attach to;

(6) Cultivation of larvae: Before megalopa metamorphoses into juveniles, pour the ponds; then use mesh or scallop cages as attachments, and change the water volume 100% per day; during the cultivation period, divide the ponds in time according to the size of larvae Cultivate or move to earthen ponds for cultivation, and can be sold as seedlings when young.

In the above-mentioned cultivation method of early multiplication of Japonica japonica seedlings, if there is no special instruction, operations such as reasonable baiting, disease prevention and control, changing water and aerating (oxygen) are all carried out by conventional methods according to conventional needs.

In step (5) of the above-mentioned cultivation method for early multiplication of Japonica japonica seedlings, the concentration of the nystatin seawater solution used for disinfection and bathing is preferably 30 to 40 g/m ³ , and the concentration of the potassium permanganate seawater solution is preferably 8～12g/m ³ .

In the step (5) of the cultivation method of the above-mentioned Japonica early propagation seedlings, when the molting metamorphosis of the daphnia larvae is cultivated in the 6th stage, the water is not changed between the daphnia larvae I and II stages, and 8-12 cm of water is added every day. And micro-inflate; change the water from the stage III of daphnia, and gradually increase the amount of water exchange and aeration; the amount of water exchange in each period is: 15-25% for stage III of daphnia; 25-35% for stage IV of daphnia %; 45% to 55% in the V stage of daphnia; 75 to 85% in the VI stage of daphnia; the temperature difference is less than 0.5°C when changing water; the late stage of daphnia VI begins to inflate strongly until the pool water is boiling.

Compared with the prior art, the present invention aims at the reproductive biological characteristics of the Japanese crab, and utilizes the existing facilities of industrialized seedling cultivation of the river crab to cultivate the early multiplication seedlings of the Japanese crab required for breeding and production. The early multiplication seedlings obtained by the invention can have a longer growth period than natural seedlings, and the size will be larger when they are on the market, which can significantly improve economic benefits. The present invention creates a new way of artificial early multiplication of seedlings for the seed source of seawater cultured Japanese clams, can provide sufficient and high-quality Japanese clams seedlings for coastal aquaculture farmers, fully utilizes shrimp and crab nursery facilities and seawater culture ponds, and improves The economic benefits of mariculture in the coastal areas of Jiangsu Province and Shandong and other neighboring provinces have important economic and social significance in promoting fishermen to increase their income and get rich and solve employment.

Detailed ways

The specific technical solutions of the present invention are further described below, so that those skilled in the art can further understand the present invention, without limiting their rights.

Example 1. A kind of cultivating method of early multiplication seedling of Japanese catfish, its step is as follows:

(1) Cultivation pond preparation: use potassium permanganate to disinfect the cultivation pond, rinse the cultivation pond with seawater after disinfection to remove potassium permanganate; then pave the sand with a thickness of 8cm on the 1/2 area at the bottom of the cultivation pond. There is a drainage outlet on the cultivation pond at the sand spreading place; use sterilized tiles, hollow bricks or bamboo rafts to build shelters at the bottom of the sand cultivation pond for parent crabs to inhabit; inject deep 60cm, salinity 26, pH into the cultivation pond 8.1 seawater;

(2) Cultivation of brood crabs: Take Japanese crab brood crabs with strong physique, complete appendages, and a shell length of more than 5cm. The ratio of male to female is 3:1. Cultivate brood crabs in the breeding pond with a breeding density of 2/m ² ; during the cultivation of brood crabs, light <1000 lux, and slightly inflate; when breeding brood crabs, breed them at natural water temperature for 2 days; then increase the temperature by 0.5°C per day. After reaching 14°C, maintain constant temperature cultivation, and the cultivation time at this stage is 25 days; then further increase the water temperature to 20°C and cultivate for 15 days; during the cultivation, feed the bait mainly with fresh shellfish, and the amount of bait fed is 1/2 of the body weight of the parent crab. 10%; move the brood crabs with eggs to the holding pond;

(3) Cultivation of oviposit crabs: The setting conditions of the oviposit crab temporary breeding pool are the same as those in the cultivation pond, or no sanding; the oviposit crabs enter the pool after being sterilized; they are cultured at natural water temperature for 2 days; Maintain constant temperature cultivation after 23°C, and cultivate at this stage for 12 days; the amount of bait fed is 2% of the body weight of oviposit crabs; check the development of embryos, when the embryos are dark gray and black, and the heartbeat reaches an average of 170 times/min, prepare to move to the pond;

(4) Nursery pool preparation: Disinfect the nursery pool with potassium permanganate. After disinfection, use 200-mesh sieve silk screen to filter seawater to flush the nursery pool to remove potassium permanganate, and inject 200-mesh sieve silk screen to filter seawater to water depth in the nursery pool. 70cm, the initial water temperature is 23°C, then add 2g/m ³ EDTA ₂ Na salt to eliminate heavy metal ions, and then add Unicellular algae to a density of 120,000/m ³ water body, and hang cages in the nursery pond;

(5) Cultivation of larvae: With nystatin or potassium permanganate seawater solution, the oviposit crabs prepared in step (3) to move the pool are disinfected and bathed, then washed with seawater and then put into cages to row young, and each cage is put in one, And put the eggs with similar color in the same pond; when the larvae density in the nursery pond reaches 100,000/m ³ water body, move the oviposit crabs to another nursery pond and continue to row young; After molting and metamorphosis, megalopa will develop into megalopa, and megalopa will metamorphose into stage I juvenile crabs after cultivation; after each stage of daphnia molting and metamorphosis, increase the water temperature by 0.5°C; after all metamorphosis into megalopa, stop heating to lower the water temperature Gradually lower to natural water temperature; light intensity for larvae cultivation is 3000 lux, water salinity 26, pH 8.1; water change, aeration and feeding are carried out as required during cultivation; Set up polyethylene mesh or scallop culture cages in the middle for the larvae to attach to;

(6) Cultivation of larvae: Before megalopa metamorphoses into juveniles, pour the ponds; then use mesh or scallop cages as attachments, and change the water volume 100% per day; during the cultivation period, divide the ponds in time according to the size of larvae Cultivate or move to earthen ponds for cultivation, and can be sold as seedlings when young.

Example 2. A kind of cultivating method of early multiplication seedling of Japanese catfish, its step is as follows:

(1) Cultivate pond preparation: use potassium permanganate to disinfect the cultivation pond, wash and remove potassium permanganate with seawater after the disinfection; then lay 15cm sand with a thickness on the 3/4 area at the bottom of the cultivation pond. There is a drainage port on the cultivation pond at the sand spreading place; use sterilized tiles, hollow bricks or bamboo rafts to build a shelter at the bottom of the sand cultivation pond for the parent crabs to inhabit; inject deep 80cm, salinity 30, pH into the cultivation pond 8.5 seawater;

(2) Cultivation of brood crabs: Take Japanese crab brood crabs with strong physique, complete appendages, and shell length of more than 5cm. The ratio of male to female is 3:1. Cultivate parent crabs in the breeding pool with a breeding density of 3/m ² ; during the cultivation of parent crabs, the light is less than 1000 lux, and a small amount of air is added; when breeding parent crabs, they are first cultured at natural water temperature for 3 days; After reaching 14°C, maintain constant temperature cultivation, and the cultivation time at this stage is 20 days; then further increase the water temperature to 20°C and cultivate for 20 days; during the cultivation, feed the bait mainly composed of fresh shellfish, and the amount of bait fed is 1% of the parent crab's weight. 25%; move the brood crabs with eggs to the holding pond;

(3) Cultivation of oviposit crabs: The setting conditions of the oviposit crab temporary breeding pond are the same as those in the cultivation pond, or no sanding; the oviposit crabs enter the pool after being sterilized; they are cultivated at natural water temperature for 3 days; After reaching 23°C, maintain constant temperature cultivation, and cultivate for 14 days at this stage; the amount of bait to be fed is 10% of the body weight of oviposit crabs; check the development of embryos, when the embryos are dark gray and black, and the heartbeat reaches an average of 180 times/min, prepare to move to the pond ;

(4) Nursery pool preparation: Disinfect the nursery pool with potassium permanganate. After disinfection, use 200-mesh sieve silk screen to filter seawater to flush the nursery pool to remove potassium permanganate, and inject 200-mesh sieve silk screen to filter seawater to water depth in the nursery pool. 80cm, the initial water temperature is 23°C, then add 5g/m ³ EDTA ₂ Na salt to eliminate heavy metal ions, and then add Unicellular algae to a density of 150,000/m ³ water body, and hang cages in the nursery pond;

(5) Cultivation of larvae: With nystatin or potassium permanganate seawater solution, the oviposit crabs prepared in step (3) to move the pool are disinfected and bathed, then washed with seawater and then put into cages to row young, and each cage is put in one, And put the eggs with similar color in the same pond; when the larvae density in the nursery pond reaches 150,000/m ³ water body, move the oviposit crabs to another nursery pond and continue to row young; After the metamorphosis, the megalopa will develop into a megalopa, and the megalopa will metamorphose into a stage I juvenile crab after being cultivated; after each stage of the molt metamorphosis, the water temperature will be increased by 1°C; Gradually lower to natural water temperature; light intensity for larvae cultivation is 10000 lux, water salinity 27, pH 8.4; water change, aeration and feeding are carried out as needed during cultivation; Set up polyethylene mesh or scallop culture cages in the middle for the larvae to attach to;

(6) Cultivation of larvae: Before megalopa metamorphoses into juveniles, pour the ponds; then use mesh or scallop cages as attachments, and change the water volume 100% per day; during the cultivation period, divide the ponds in time according to the size of larvae Cultivate or move to earthen ponds for cultivation, and can be sold as seedlings when young.

Example 3. In the step (5) of the method for cultivating early breeding seedlings of Japanese crabapple described in embodiment 1 or 2, the concentration of the nystatin seawater solution for the disinfection bath is 30～40g/m ³ , the concentration of the potassium permanganate seawater solution 8-12g/m ³ .

Example 4. In the step (5) of the method for cultivating early breeding seedlings of Japanese japonica described in embodiment 1 or 2 or 3, when the molting metamorphosis of the 6 stages of the larvae was cultivated, the larvae did not change the water during the 1st stage and the 2nd stage. Add 8-12cm of water per day and slightly inflate; change the water from the stage III of daphnia, and gradually increase the amount of water exchange and aeration; 25-35% in the stage of daphnia; 45-55% in the V stage of daphnia; .

Example 5. Experiments on the breeding method of early multiplication seedlings of Japanese catfish.

1 Materials and methods

1.1 Cultivation facilities

Utilize the existing equipment in the river crab nursery, including cultivation ponds, sedimentation ponds, boilers, Roots blowers, etc. The cultivation pool was disinfected with 30g/m ³ potassium permanganate for several hours, and then rinsed with filtered seawater. The 2/3 area at the bottom of the pool is covered with 10cm thick fine sand to facilitate mating and spawning of brood crabs. A 1/3 open space is left near the drain for feeding, changing water and removing residual bait. Japanese crabs have a fierce temperament and are prone to injury due to fighting with each other. Therefore, shelters must be placed in the brood crab breeding ponds, which can be built with sterilized tiles, hollow bricks or bamboo rafts.

1.2 Selection of parent crabs

On March 2, 2009, 135 female crabs and 45 male crabs with strong physique and complete appendages were purchased. Because the gonad development of crustaceans is limited by individual size, it is advisable to choose those with a shell length of 5 cm or more when selecting parent crabs. During transportation, use rubber bands to wrap the claws of the parent crabs, layer them into multi-layer crab cages, and then put them into a bucket filled with clean sea water, transport them with oxygen or wrap the parent crabs in a foam box with a wet towel Dry transport.

1.3 Cultivation method of parent crabs

1.3.1 Preparation of the breeding pond and release of brood crabs The depth of water in the breeding pond is 70cm, the salinity is 26-30, and the pH is 8.1-8.5. Parent crabs need to be disinfected before entering the pool, soaked in 200-300mg/L formalin for 10 minutes, rinsed with clean water, and put into the cultivation pool. The breeding density of brood crabs is 2-3/m ² . Illumination <1000 Lux, slightly inflated.

1.3.2 Ways of warming up: The water temperature of parent crabs entering the pool at the beginning of March is 4-5°C, and the parent crabs are cultured at natural water temperature for 3 days to adapt to the new environment, and then the temperature is raised to 14°C at a daily temperature increase of 0.5-1°C. From the end of March to the beginning of April, the water temperature is further gradually raised to 20°C.

1.3.3 Feeding Feed once a day in the morning and evening, mainly in the evening, and the bait is mainly fresh shellfish, with a certain amount of live clamworm, miscellaneous fish, shrimp, etc., the amount of feeding is parent 10-25% of the crab's body weight, adjusted accordingly according to the feeding situation. The bait is placed at the bottom of the pond without sand, which is convenient for feeding and cleaning.

1.3.4 Water quality management Absorb sewage and change water once a day. Sprinkle flufenac or rifampicin 1g/m ³ and formaldehyde 20g/m ³ regularly to inhibit the growth of bacteria and parasites. Take out the brood crabs once a week and disinfect the sand at the bottom of the pool with potassium permanganate or formaldehyde, wash away the residual drugs and add water, then put the brood crabs.

1.4 Cultivation of oviposit crabs

Before entering the pool, the egg-bearing crabs are soaked in 200-300 mg/L formalin for 10 minutes, rinsed with clean water, and put into the holding pool. The breeding density of oviposit crabs is 2-3/m ² . Breeding crabs at natural water temperature for 3 days to adapt to the new environment, and then maintain constant temperature cultivation at a daily temperature increase of 0.5-1°C to 23°C. Feed once a day in the morning and evening, mainly in the evening, feed fresh scallop meat, live clam worms and other bait that Japanese moths like to eat and are rich in nutrients. The situation is adjusted accordingly. The water depth of the cultivation pool is 70cm, the salinity is 26-30, and the pH is 8.1-8.5. It absorbs sewage and changes water every day, the light is less than 1000 lux, and aerated slightly. Sprinkle flufenac or rifampicin 1g/m ³ and formaldehyde 20g/m ³ regularly to inhibit the growth of bacteria and parasites. Check the development of the embryo every day. As the development progresses, the egg color gradually becomes darker, from orange to yellowish brown to light gray to gray black. When the embryo is dark gray and black, the heartbeat reaches an average of 180 beats/min, and the daphnia-like larvae in the membrane twist frequently, it indicates that hatching is imminent.

1.5 Larval hatching

Sterilize the nursery ponds with 30g/m ³ potassium permanganate for several hours before laying the ponds, then use 200-mesh sieves to filter the seawater and wash it clean, then enter the water, the water depth is 80cm, the water temperature is 23°C, and 2-5g/m ³ EDTA ₂ is added Na salt to eliminate the toxicity of heavy metal ions to larvae. Put chaetoceros, golden algae and other single-celled algae at a density of 150,000/m ³ water body, and put them in advance so that the hatched Z1 can get enough bait. Oviposit crabs are soaked in 40g/m ³ nystatin or potassium permanganate 10g/m ³ for 30 minutes, cleaned, hung in cages and rowed in nursery ponds. 5 to 8 cages are hung in each pool, and one egg-bearing crab is placed in each cage, and the eggs with similar color are placed in the same pool, so that the platoons are basically synchronized. When the larvae density in the nursery pond reaches 150,000/m ³ water body, the oviposit crab is moved to another nursery pond to continue rowing young.

1.6 Cultivation of larvae

Japonica larvae are divided into 6 stages. Under the water temperature of 23-26°C, they molt and metamorphose once every 3-4 days, and develop into megalopa in about 20 days. After 5-6 days of cultivation, megalopa metamorphoses into I Juvenile crabs.

After each daphnia larva molts and metamorphoses, increase the water temperature by about 0.5-1°C to promote its development. After all metamorphosis into megalopa, stop heating to make the water temperature gradually drop to the same temperature as the outside water. The light intensity should be controlled at 3,000-10,000 lux, and direct strong light should be avoided, so as not to cause phototaxis of larvae and increase the probability of mutual destruction. The salinity of the water body is 26-27, and the pH is 8.1-8.4. During Z1 and Z2, do not change the water, add 10cm of water every day and slightly inflate. Change the water from the Z3 period, and gradually increase the amount of water change and air inflation. The amount of water change in each period is: Z3-20%; Z4-30%; Z5-50%; Z6-80%; M-100%. When changing water, the temperature difference is less than 0.5°C. In the later stage of Z6, it started to be strongly inflated, and the water in the pool was boiling.

In the Z1 and Z2 phases, the monocellular algae (200,000-300,000/m ³ ) are the main species, supplemented by a small amount of egg yolk (1/m ³ ), rotifers (5-10/m 3 ), etc. From Z3 to Z6, feed Artemia nauplii (100,000 to 500,000/m ³ ); add appropriate amount of copepods in the later stage of Z5. In the M period, feed minced shrimp, shellfish or fish, about 50-80g/10,000. The amount of feeding in each period is flexibly controlled by the feeding situation of the larvae and the residual bait in the water, and the feeding is 6 to 8 times a day.

After daphnia metamorphosis is megalopa, erect polyethylene mesh sheet in the pond, mesh 3mm, mesh sheet length is equal to the width of pond, and height is shorter than pond depth 3cm, and the lower end is fixed, and each pond hangs 4 pieces, For larvae to attach and reduce mutual killing. Regular use of oxytetracycline, norfloxacin and other drugs, the dosage is 1-2g/m ³ , to inhibit the production of various germs.

1.7 Cultivation of larvae

Before the megalopa metamorphoses into juveniles, pour the pond. Sterilized mesh or scallop cages are still used as attachments, the daily water change is 100%, and artemia adults and minced fresh fish and shrimp are thrown 4 times a day. During the cultivation period, according to the size of the juveniles, they are divided into ponds for cultivation or moved to earthen ponds for cultivation.

The metamorphosis survival rate of No. I-III seedling ponds (15m ³ in volume, 6.75 million juveniles in total) was statistically analyzed in detail, and compared with the seedlings raised by purchased oviposit crabs in May and June 2008.

2 Test results and discussion

2.1 During the cultivation period, a total of 24 parent crabs died, with a survival rate of 86.7%. On April 16, parent crabs began to lay eggs, one month earlier than in natural sea areas. As of April 22, a total of 84 female crabs had eggs, and the egg holding rate was 62.2% of the total number of female crabs. The average number of brood eggs is 187,000 per bird.

Temperature is an important factor affecting the gonad development of aquaculture animals. Raising the temperature can increase the metabolic rate of organisms and accelerate the development of gonads, so it has become a commonly used technical means in the breeding and production of aquatic animal seedlings. The results of this experiment show that Japanese kale can also mature and conceive eggs earlier under the condition of artificial temperature control, which can prolong the growing time and provide favorable conditions for growing large-scale in the same year. In the specific operation process of temperature rise, it should be noted that the temperature should be raised to 14°C at the beginning of the temperature rise, and then continue to rise to 20°C after a certain period of time, because Japanese carp can have a large food intake at 14°C, and at the same time can make eggs The yolk substance in the mother cell is fully synthesized and accumulated, and develops into a high-quality egg. If the temperature is directly raised to 20°C, the gonads will develop too fast, the yolk deposition in the eggs will be insufficient, the eggs produced will be small, and the quality of the seed will be greatly affected. In addition, if the temperature rise is too large and too high, it will cause adverse stress reactions of parent crabs and lead to gonad degeneration.

The material basis for gonad development comes from bait, so while raising the temperature, it is necessary to ensure the nutrient supply of parent crabs. The baits fed in this experiment are of various types, and their nutritional components can complement each other, which is more comprehensive than that of a single bait. Fresh shellfish meat, live clamworm, fish and shrimp meat, etc. are all baits rich in protein and lipid, which meet the needs of gonad development and yolk synthesis of parent crabs. In particular, clam worms are rich in highly unsaturated fatty acids - eicosadonic acid, which is closely related to the synthesis of hormones that control gonad development in crustaceans, so feeding live clam worms can not only promote the gonad development of parent crabs, but also Will not pollute water quality. The amount of bait feeding should be flexibly controlled according to the daily residual bait situation, and it is advisable to have a little surplus.

Japonica is aggressive by nature, and excessively high breeding density will cause mutilation and injury, which will reduce the survival rate. The appropriate breeding density of brood crabs is 2-3/m ² . At the same time, shelters are placed in the brood crab breeding ponds to reduce the probability of their fratricide.

2.2 During the breeding period, a total of 11 oviposit crabs died, with a survival rate of 86.9%. After 14 days of cultivation, the larvae were released on May 6. See Table 1 for the survival of the larvae.

Table 1 Survival of larvae at each stage during the cultivation of larvae in Japan

Note: I represents the larvae discharged from the oviposit crabs obtained through intensive cultivation in this test; II represents the larvae discharged from the oviposit crabs purchased in May 2008; III represents the larvae discharged from the oviposit crabs purchased in June 2008; the number of larvae at each stage This is the average of the daily counts of larvae; the survival rate is the calculated result from Z1 to each stage of larvae. The data in the table were subjected to one-way ANOVA and Duncan test, and different lowercase letters in superscripts indicate significant differences between groups (P<0.05).

As can be seen from Table 1, 1.35 million megalopa larvae were obtained in 3 nursery ponds using the larvae discharged from the oviposit crab obtained through intensive cultivation, with an average unit water density of 30,000 and a survival rate of 20.0%. In May 2008, 1.4 million megalopa were obtained from the larvae discharged from the purchased oviposit crabs. The average unit water density was 31,100, and the survival rate was 20.7%, slightly higher than the former. The larvae discharged from the oviposit crab purchased in June were used for cultivation. The survival rate of larvae at each stage was significantly lower than that of the first two groups. Only 900,000 megalopa were obtained, with an average unit water density of 20,000 and a survival rate of 13.3%. . This batch of larvae was cultivated from late June to late July, entering a period of high temperature, coupled with the impact of heavy rains and red tides, which deteriorated the water quality of sea water. Although the influent was treated with sedimentation and filtration, the survival rate of larvae was still low, and this batch of oviposit crabs The survival rate of the temporary culture is also lower than that in May, so the artificial seedlings of Japanese catfish should be raised sooner rather than later, which can avoid the impact of high water temperature and deterioration of water quality.

2.3 In the three nursery ponds where the larvae of group II were cultivated, the megalopa in the two nursery ponds erected with polyethylene mesh were cultivated for 6 days, and about 200,000 young crabs were obtained in the first stage, and the average unit water density was 13,300 Only, the metamorphosis rate reached 42.9%. The megalopa in the control pond without the net sheet all lie on the bottom of the pond, and only 50,000 stage I juvenile crabs are obtained, the average unit water density is 0.33 million, and the metamorphosis rate is only 10.7%. It shows that the phenomenon of mutual mutilation among megalopa is serious, and attachments must be placed for them to climb, so as to reduce the mutual mutilation rate. Those who have the conditions can use scallop culture cages instead of mesh, and the effect is better. At the same time, increase the amount of inflation and ensure sufficient supply of bait.

Claims (3)

1. a method for cultivating early breeding seedlings of japonica, is characterized in that, its steps are as follows: (1) Preparation of cultivation pond: Disinfect the cultivation pond with potassium permanganate. After disinfection, wash the cultivation pond with sea water to remove potassium permanganate; ～15cm of sand, and there is a drainage outlet on the cultivation pond where the sand is not spread; use sterilized tiles, hollow bricks or bamboo rafts to build shelters at the bottom of the sand-sprayed cultivation pond for the parent crabs to inhabit; inject deep 60 cm into the cultivation pond. ～80cm seawater with salinity 26～30 and pH 8.1～8.5; (2) Cultivation of brood crabs: Take Japanese crab brood crabs with strong physique, complete appendages, and a shell length of more than 5cm. The ratio of male to female is 3:1, and sterilize them by soaking in 200-300mg/L formalin seawater solution and rinse with clean water. Afterwards, put them into the breeding pool for parent crab cultivation, and the cultivation density is 2 to 3/m ² ; during the parent crab cultivation period, the light is less than 1000 lux, and a small amount of air is added; when the parent crabs are cultivated, they are first cultured at natural water temperature for 2 to 3 days; Raise the temperature by 0.5-1°C to 14°C and then maintain constant temperature cultivation. The whole stage of temperature rise and constant temperature cultivation takes 20-25 days; then further increase the water temperature to 20°C and cultivate for 15-20 days; Shellfish-based bait, the amount of bait feeding is 10-25% of the parent crab's body weight; move the parent crabs with eggs to the holding pond; (3) Cultivation of oviposit crabs: the setting conditions of the oviposit crab temporary breeding pond are the same as those in the cultivation pond, or without sanding; the oviposit crabs enter the pool after being sterilized; they are cultured at natural water temperature for 2 to 3 days; After the range of ℃ rises to 23 ℃, maintain constant temperature cultivation, and cultivate for 12 to 14 days during the whole stage of heating and constant temperature; the amount of bait fed is 2 to 10% of the body weight of oviposit crabs; check the development of embryos, when the embryos are dark gray and black, heartbeat When it reaches an average of 170-180 times/min, prepare to move the pool; (4) Nursery pool preparation: Disinfect the nursery pool with potassium permanganate. After disinfection, use 200-mesh sieve silk screen to filter seawater to flush the nursery pool to remove potassium permanganate, and inject 200-mesh sieve silk screen to filter seawater to water depth in the nursery pool. 70-80cm, the initial water temperature is 22-23°C, then add 2-5g/m ³ EDTA ₂ Na salt to eliminate heavy metal ions, and then add unicellular algae to a density of 120,000-150,000/m ³ water body, and hang them in the nursery pool cage; (5) Cultivation of larvae: With nystatin or potassium permanganate seawater solution, the oviposit crabs prepared in step (3) to move the pool are disinfected and bathed, then washed with seawater and then put into cages to row young, and each cage is put in one, And put eggs with similar color in the same pond; when the density of larvae in the nursery pond reaches 100,000 to 150,000/m ³ water body, move the oviposit crabs to another nursery pond and continue to row young; After the 6th stage of molting metamorphosis, it develops into megalopa, and the megalopa metamorphoses into stage I juvenile crabs after cultivation; after each stage of molt metamorphosis, the water temperature is increased by 0.5-1°C; after all metamorphosis into megalopa, stop Heat the water to gradually reduce the water temperature to the natural water temperature; the light intensity for larvae cultivation is 3000-10000 lux, the water salinity is 26-27, and the pH is 8.1-8.4; when cultivating, change water, aerate and feed as needed; when daphnia larvae After metamorphosis into megalopa, set up polyethylene mesh or scallop culture cages in the nursery pond for the larvae to attach to; (6) Cultivation of larvae: Before megalopa metamorphoses into juveniles, pour the ponds; then use mesh or scallop cages as attachments, and change the water volume 100% per day; during the cultivation period, divide the ponds in time according to the size of larvae Cultivate or move to earthen ponds for cultivation, and can be sold as seedlings when young. 2. the method for cultivating early propagation seedlings of Japanese catfish according to claim 1, characterized in that, in step (5), the concentration of the nystatin seawater solution used for disinfection bathing is 30～40g/m ³ , high manganese The concentration of potassium acid potassium seawater solution is 8-12g/m ³ . 3. the method for cultivating of the early breeding seedlings of Japanese japonica according to claim 1, is characterized in that, in step (5), when daphnia larvae 6 phases of moulting metamorphosis are cultivated, during the daphnia larvae I phase and II phase, there is no Change the water, add 8-12cm of water every day and slightly inflate; start changing the water from the third stage of daphnia, and gradually increase the amount of water and air; 25-35% in the IV stage of daphnia; 45-55% in the V stage of daphnia; 75-85% in the VI stage of dapa; The water in the pool is boiling.